In the six Arrow heads, there is one Arrow which is different than the others. 5 have holes while the 6th has a bug thing attached instead.

Incidentally that Arrow was the one giving people Requiem Stands. Could it be that this 6th Arrow could be a superior version which can unlock further power for Stands? Could explain the utter lack of Requiem Stands in other parts.

I guess it kinda makes sense, because Golden Experience was stabbed by Black Sabbath's Arrow early on and nothing changed. I suppose it's worth mentioning the different design of the Arrow without any speculation.

There are a couple of things i cab argue here:
First, in order to get a Requiem, one has to be stabbed for several seconds, like when Silver Chariot was stabbed yet only for a small period of time with this arrow.
Second, they are all made from the same material, and it would make sense if this arrow looked different just because it has more importance in the story than others.

Perhaps its a matter of willpower and desire that is needed to make an Arrow stab someone for the second time (be it User or Stand) and reactivate its power to awaken a new ability within the being it stabbed?